Abstract

The temperature behavior of the first critical field of superconducting thin film samples can be determined with high accuracy using an inductive and contactless method. Driving a sinusoidal current in a single coil placed in front of the sample, a nonzero third harmonic voltage is induced in it when Abrikosov vortices enter the sample. Conditions to be satisfied for the quantitative evaluation of using this technique are detailed. As a validation test, different type II superconductors (Nb, NbN, , and under the form of thin films) have been measured. The comparison between experimental results, data presented in literature, and theoretical predictions is presented and discussed.

Received 27 November 2008Accepted 27 July 2009Published online 02 September 2009

Acknowledgments:

We are grateful to P. Orgiani and R. Russo for providing us and Nb film samples. We would like to thank A. Gurevich, M. Polichetti, J. Halbritter, E.H. Brandt, and Y. Mawatari for fruitful discussions and suggestions. We thank S. Zocco (Casale Bauer) for providing us the linear power amplifier SAMSON SX1200 and for fruitful discussions. We are indebted to V. De Luise for his valuable technical assistance. We acknowledge financial support of the Italian Foreign Affairs Ministry (MAE) - General Direction for the Cultural Promotion.